rendering: migrate object id shader to unity-style single source

engine/assets/builtin/shaders/object-id/object-id.shader

@@ -6,16 +6,44 @@ Shader "Builtin Object Id"
         {
             Name "ObjectId"
             Tags { "LightMode" = "ObjectId" }
-            Resources
-            {
-                PerObjectConstants (ConstantBuffer, 0, 0) [Semantic(PerObject)]
-            }
+            Cull Back
+            ZWrite On
+            ZTest LEqual
             HLSLPROGRAM
+            #pragma target 4.5
             #pragma vertex MainVS
             #pragma fragment MainPS
-            #pragma backend D3D12 HLSL "object-id.vs.hlsl" "object-id.ps.hlsl" vs_5_0 ps_5_0
-            #pragma backend OpenGL GLSL "object-id.vert.glsl" "object-id.frag.glsl"
-            #pragma backend Vulkan GLSL "object-id.vert.vk.glsl" "object-id.frag.vk.glsl"
+            cbuffer PerObjectConstants : register(b0)
+            {
+                float4x4 gProjectionMatrix;
+                float4x4 gViewMatrix;
+                float4x4 gModelMatrix;
+                float4 gObjectIdColor;
+            };
+
+            struct VSInput
+            {
+                float3 position : POSITION;
+            };
+
+            struct PSInput
+            {
+                float4 position : SV_POSITION;
+            };
+
+            PSInput MainVS(VSInput input)
+            {
+                PSInput output;
+                const float4 positionWS = mul(gModelMatrix, float4(input.position, 1.0));
+                const float4 positionVS = mul(gViewMatrix, positionWS);
+                output.position = mul(gProjectionMatrix, positionVS);
+                return output;
+            }
+
+            float4 MainPS(PSInput input) : SV_TARGET
+            {
+                return gObjectIdColor;
+            }
             ENDHLSL
         }
     }